Silyl enol ethers are important synthetic intermediates for organic synthesis, and can be used as a synthetic intermediate for pharmaceutical products and organic materials, or a treatment agent in various fields of surface treatment.
Representative general production methods of a silyl enol ether using ketone (or aldehyde) as a starting material are three methods shown below.



Method (A) is a method most generally used, which requires a stoichiometric amount of reactants and, as a result, produces a stoichiometric amount of amine and lithium halide as a waste. Generally, moreover, low temperature conditions are required during preparation of lithium enolate. Method (B) is considered to be a comparatively convenient method; however, it is difficult to apply except for the synthesis of trimethylsilyl enol ether (R4A-R6A=Me). In this case, again, a stoichiometric amount of an amine/hydrogen halide salt is produced as a waste. As a reaction temperature, a high temperature of not less than 100° C. is often required. Method (C) is also a comparatively convenient method, and the reaction temperature is around room temperature. In this case, again, produced as a waste is a stoichiometric amount of an amine/hydrogen halide salt and sodium chloride. Depending on the substrate, the reaction may not proceed sufficiently.
Methods (1) to (4) shown below have been further reported the production methods of a silyl enol ether.    (1) Chemical Communications, 2002, pp. 1628-1629 (non-patent document 1)
    (2) JP-A-11-217391 (patent document 1)
    (3) Journal of Organic Chemistry, 1981, Vol. 46, pp. 5212-5214 (non-patent document 2)
    (4) JP-A-11-116582 (patent document 2)

Method (1) is a synthesis method using a stoichiometric amount of N-methyl-N-(trimethylsilyl)acetamide as a silylating agent in the presence of a catalytic amount of a base. As a waste, a stoichiometric amount of N-methylacetamide and a trace amount of a hydrogen gas are produced. However, it has a problem in that preparation of a silylating agent (N-methyl-N-(trimethylsilyl)acetamide) used here results in the production of a stoichiometric amount of a salt of a base and hydrogen halide as a waste. In addition, handling of the silylating agent is not easy.
Method (2) is a method using a catalytic amount of groups 7 to 10 transition metal catalysts, ethyl iodide and ethylamine, and a stoichiometric amount of silane (silyl hydride). The waste in this method is considered to be less as compared to the above-mentioned methods (A) to (C). However, it discharges a trace amount of a transition metal and an amine/hydrogen halide salt which place high environmental load. In addition, the co-presence of a transition metal and a hydrogen gas may be dangerous since it sometimes causes explosion.
Method (3) is a method using 1.5 equivalents of allylsilane, 1.5 equivalents of trifluoromethanesulfonic acid and 2 equivalents of triethylamine as reactants relative to ketone as a starting material. In this case, ketone as a starting material and triethylamine need to be added after preparation of a chemically active species by blending allylsilane and trifluoromethanesulfonic acid, and the operation process is complicated. In addition, a high number of waste materials are produced in a stoichiometric amount.
Method (4) has a problem in that the starting material is limited to a 1,3-dicarbonyl compound alone besides production of a stoichiometric amount of amine.
Taking all these aspects into consideration, when an organic compound is produced in a large amount, a reaction producing the least possible waste (coproduct) is desirable. In addition, there is a problem in that hydrogen halide generated not only corrodes reactors and incineration system, but also places a high environmental load. Therefore, the development of a method to solve the problem has been desired.